Nuclear fuel bodies and the production thereof

Abstract

A nuclear fuel body provided by doped uranium dioxide grains having kernels of undoped uranium dioxide. The body is produced by mixing single crystal seeds of uranium dioxide with doped uranium dioxide granules. The mixture is compacted and subsequently sintered. Gadolinia is a preferred dopant for the uranium dioxide.

I claim: 
     
       1. A method of producing a nuclear fuel body, the method comprising mixing single crystal seeds of uranium dioxide with granules comprising doped uranium dioxide, compacting the mixed seeds and granules, and sintering the compacted mixed seeds and granules, whereby a nuclear fuel body is produced comprising doped uranium dioxide grains having kernels comprising undoped uranium dioxide. 
     
     
       2. A method as claimed in claim 1, wherein the doped uranium dioxide comprises UO 2  -Gd 2  O 3 . 
     
     
       3. A method as claimed in claim 2 wherein the seeds comprise between 2 and 5% by weight of the mixed seeds and granules. 
     
     
       4. A method as claimed in claim 3, wherein the Gd 2  O 3  comprises about 8% by weight of the UO 2  -Gd 2  O 3 . 
     
     
       5. A method as claimed in claim 1, wherein the sintering is performed in an environment comprising a reducing atmosphere. 
     
     
       6. A method as claimed in claim 5, wherein the reducing atmosphere comprises wet hydrogen/nitrogen at about 1720° C. 
     
     
       7. A method of producing a nuclear fuel body, the method comprising obtaining single crystal uranium dioxide seeds, forming a mixture of the seeds with uranium dioxide granules doped with about 8% by weight gadolinia, the seed content in the mixture being about 2% by weight, pressing the mixture at about 4 t.cm -2  to form a body, and sintering the body in an atmosphere of wet hydrogen/nitrogen for about 12 hours at about 1720° C., whereby a nuclear fuel body is produced comprising doped uranium dioxide grains having kernels comprising undoped uranium dioxide. 
     
     
       8. A nuclear fuel body made by the method of claim 1. 
     
     
       9. A nuclear fuel body made by the method of claim 7.